Horizontal continuous casting apparatus



July 4, 1967V R, T, CRA@ 3,329,200

HORIZONTAL CONTINUOUS CASTING APARATUS PRIOR ART |8\ g1g/ij L// als als 20s 209 ATWToRNgY July 4, 1967 R. T. CRAIG HORIZONTAL CONTINUOUS CASTING APPARATUS 2 sheets-sheet 2 Filed Jan. 5, 1965 R @@m mT n, lm A /0 c 00K Wm a IO E 840 BIO Soslo United States Patent O 3,329,200 HORIZONTAL CONTINUOUS CASTING APPARATUS Richard T. Craig, New Kensington, Pa., assignor to Aluminum Company of America, Pittsburgh, Pa., a

corporation of Pennsylvania Filed Jan. 5, 1965, Ser. No. 423,461 6 Claims. (Cl. 164-267) This invention relates to continuous casting in horizontally disposed molds, ingots of the light metals, aluminum and magnesium, together with alloys in which these metals constitute at least 75% by weight of the composition.

Horizontal continuous casting of ingots has found commercial acceptance because of generally recognized adv-antages in certain respects over vertical casting. For .instance, vertically casting long ingots requires elevating the mold or providing a deep pit beneath it, either method representing a costly installation which is avoided in horizontal casting. Other advantages are the degree of operating continuity and the ingot handling convenience associated with horizontal casting.

In the horizontal casting under consideration here, molten metal is provided in a reservoir separated from the horizontal mold by a partial barrier or closure which does not chill the metal, and hence can be conveniently made of an insulating or refractory material. This partial closure, hereinafter referred to as the header plate, h-as a gate, or opening, for passage of 4the liquid metal therethrough and directly into a drastically chilled mold wherein the metal is solidified and continuously with drawn in a horizontal direction. The emerging ingot is then conveniently cut to desired lentgh without interrupting the casting operation, the duration of a casting run depending only on the molten metal supply.

Horizontally cast light metal ingots often exhibit fa surface defect called a lap or fold which corresponds to what is called a cold-shut in vertically cast ingots. These lap defects, as explained in more detail hereinafter, appear as repeated band-like irregularities on the ingot surface normal to the axis of the ingot and are generally attributed to variations in surface tension and metal freezing rates which occur during initial contact of the metal with the drastically chilled mold. The laps or folds extend into or penetrate the surface of the ingot which generally necessitates removal of the affected surface portions to an extent commensurate `with the depth of penetration before the ingot is further processed especially if it is lto be rolled. The lap penetration problem is generally most severe in horizontally cast ingots having relatively large cross-sections where the lap depth or penetration varies from less than 1A" in the top-most surface portion of the ingot to or 1/z or even more in the lower surface portions of the ingot. The difference in depth of the laps on the bottom and top sur faces of an ingot is considered to be disproportionate. While there are some exceptions, this severe or disproportionate lap penetration is most often observed in light metal alloys having a relatively wide freezing range. While the foregoing condition in the top-most surface portion of the ingot is often considered commercially acceptable from the standpoint of the depth of metal to be removed, the deeper cut associ-ated with the lower surface portions is generally deemed excessive.

It has been discovered that the severe lap penetration prevailing in the lower surface portions of a horizontally cast ingot can be alleviated by providing a suitably disposed non-chilling surface which'interrupts excessive lap penetration. This surface is most conveniently situated on the mold-side face of the header plate.

3,329,200 Patented July 4, 1967 Accordingly a primary object of the invention is to provide apparatus adapted to minimize disproportionate lap penetration into the freezing ingot surface, especially at the lower surface portions thereof, in the continuous horizontal casting of light metal ingots.

Another object of the invention is to provide a method for continuously casting light metal ingots in horizontally disposed molds wherein lap penetration, particularly in the surface of the lower ingot portions, is minimized.

Further objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

For a `better understanding of the invention and its objects reference is made to the following description, including the appended claims and the drawings in which:

FIGURE 1 is an elevational view, partly in crosssection, illustrating a horizontal casting apparatus;

FIGURE 2 is an enlarged longitudinal cross-section of the lower portion of a metal ingot freezing in a horizoltal mold;

FIGURE 3 is an isometric view, partially in cross'- section, illustrating an embodiment of the invention as applied to casting an ingot having ya liat side;

FIGURES 4a, 4b and 5 are cross-sectional views illustratin g variations of the invention;

FIGURES 6 and 7 are elevational cross-sections illustrating, in more detail, embodiments of the invention;

FIGURE 8 illustrates schematically the peripheries of three ingot cross-sections indicating the zones of severe and disproportionate lap penetration.

Briefly, the invention resides in the discovery that the severe and disproportionate lap conditions prevailing in the lower surface portions of horizontally continuous cast ingot can be minimized by the provision of a non-chilling surface, oriented signicantly off the vertical plane and situated immediately anterior to the chilling mold `and in close proximity to the inside surafce thereof. This non-chilling surface may be provided in a variety of forms, for instance a notch cut into the mold entrance closure member face on the side facing the mold, the notch being situated in close proximity -to the inner chilled mold surface and providing a significantly non-vertical surface. As explained in more detail hereinafter, this surface effects thermal and other influences upon the formation of laps and significantly curtails their extension into the body of the ingot.

Referring now to the drawings, the general larrangement of a horizontal casting apparatus embodying the invention is shown in FIGURE 1. Therein is shown an open top molten metal reservoir 2 having walls of a suitable -refractory material 6, `and having the general transverse shape of a U and of sufficient width to embrace all of gate 20 in the header plate 18. The header plate 1S consists of a vertical plate-like refractory heat insulative material having an aperture 20 to permit the transfer of metal 8 from the reservoir 22 through the header plate and into the chilled mold 10. The choice of refractory will be Idetermined by the nature of the metal being cast, in the case of casting aluminum and aluminum base alloys the commercial asbestos-silica product sold under the trade name Marinite is satisfactory. It is to be understood that while the header plate is most conveniently fashioned from refractory material, such is not `an absolute necessity. It is only essential that the header plate does not significantly chill the liquid metal before it reaches the drastically chilled mold and hence the member is described functionally in the claims as a non-chilling header plate. On the opposite side of the header plate 18 and compressed -against it in a sealing position is the chilled mold 10 which `can be made of a suitable heat conductive material such as aluminum or copper or alloys in which these metals predominate.

Although the rnold can be made as an assembly, a more convenient arrangement is to make the mold as an integral casting and machine the surfaces where required as ywell -as any passageways. The mold is generally quite short, even where large ingots are cast, typical fold lengths ranging from -about l to 4 inches. The mold has a lip or step at its entrance. This inwardly extending step may be provided by a separate metallic gasket 32 which has a slightly smaller opening than the mold yas shown. The use of such a gasket is described and claimed in copending application Ser. No. 286,349, now abandoned, and its continuation -application Ser. No. 542,424. Typical dimensions for this inwardly extending short step are about 1/16 length (gasket 32 thickness) and 0.010 step extension into the mold cavity. The mold 10 may be cooled by circulation of water or other coolant supplied through pipe 14 to chamber 16 in the mold wall. The coolant is discharged from chamber 16 and pro- -jected as a sheath 52 onto the emerging ingot through channel 50. Alternatively, the mold Without a surrounding cooling chamber may be chilled by suitably positioned Water sprays. Also seen in FIG. 1 is passageway 58 for continuously supplying lubricant to channel 34 from where it is fed to the head of the mold at the inner wall surface through suitable small openings which may be fashioned by cutting a series of radially disposed notches 33 into the mold face to connect the oil channel '34 with the .mold interior. Suitable means, not shown, are provided for refractory back-up, structural support, etc.

The molten metal supply in relation to the solidified ingot is lalso evident in FIG. 1 where molten metal 8 in the reservoir passes through the gate in the header plate 18 and establishes a molten head of metal 36 within the mold 10. It should be noted that the molten metal level in the reservoir is above the mold thereby furnishing a positive liquid head of metal. The gate opening 20 is significantly smaller than the ingot cross-section and may be provided below the ingot axis although it is spaced somewhat from the mold inside wall. Thus some molten metal moves lthrough the gate 20 and along the mold side wall 19 of the header plate 18 and contacts the chilled mold. The metal coming in contact with the mold surface freezes almost immediately to form the walls of the embryo ingot, the freezing starting at 42 next to the header plate 18. The head of molten metal generally extends beyond the exit end of the mold, the boundary between liquid or semi-liquid and solid metal being generally illustrated for the ideal case by line 38. The molten metal progressively freezes forming a solid ingot 40 which is moved away from the mold at a continuous rate by means of power actuated rollers 54, or the like. While there has been described a particular species of horizontal continuous casting apparatus, it is not intended that lthe invention be necessarily limited thereto.

At this point a brief explanation is set forth as to what are believed to be the nature and the causes of lap development in ingot casting together with how such is affected by the practice `of the invention. It is observed in FIGURE 1 that laps appear on the ingot surface as a series of bands, typified by the numeral 110, extending around the periphery of the ingot in a plane substantially normal to the ingot axis. In cross-section it is observed that the laps appear as a series of linear penetrations into the ingot and that a typical lap penetration 130 across the top-most portion of the ingot is less than that 108 at the botto-m. For clarity purposes `only a few laps are illustrated in FIG. 1; however, it is to be understood that the lap defects prevail along the entire ingot length and that those shown are merely typical. The penetration at the top is typified by depth of generally not more than about 1/s to 1A of an inch as opposed to the condition at the bottom portions where the Penetration runs as deep as 1%" to 1/2" or more in large ingots. While the precise reason for this condition is not completely understood, the zones of maximum lap penetration appear to be associated with the most drastically chilled regions which in turn are probably determined by a combination of thermal and gravitation effects. The disproportionate lap penetration problem is generally most pronounced in ingots having a relatively large transverse cross-section, for instance, a 15 by 40 rectangular cross-section. Also, while there are exceptions to this general rule, alloys having relatively broad freezing ranges (810 F. to 200 F. and higher) are generally most susceptible to the disproportionate lap penetration. FIGURE 2 is an enlarged cross-section of the lower portion of a freezing ingot emphasizing lap growth into the ingot surface. It can be seen that a band of discontinuities in grain structure and composition, schematically typified by dotted lines paralleling the lap itself and the ingot surface and designated by the numeral 209, extend a little further into the ingot than the actual lap itself and must be considered in removing surface material to prepare the ingot for further processing. The zone of severe lap penetration is described herein as the lower surface portions but also generally extends around the entire periphery excepting the top-most portion. For example FIGURE 8a illustrates the periphery of an ingot of rectangular cross-section and the zones of minimal lap penetration, the top-most surface portion 840, together with the zone of severe and disproportionate la-p penetration, the lower surface portions 810. Similarly FIGURES 8b and c respectively illustrate this zone for circular and polygonal cross-sections. Thus the terrn lower surface portions is intended to encompass this zone which not only includes the bottom itself but more often extends up the sides and generally around the top corners. p

It is believed that laps are caused by iiuctuations in the surface skin of the ingot as freezing is initiated. Referring to FIGURE 2 the liquid metal at the junction of the non-chilling or refractory header plate 18 and the mold 10 the liquid surface is shown as forming a submerged free liquid meniscus 220 which also forms the boundary -of meniscus void 210. The insert gasket 32 is not shown completely in FIG. 2 so that the meniscus effects may be more clearly illustrated. As the liquid metal is chilled, its surface becomes semi-solid, or plastic, a condition wherein it does not function as a liquid but cannot be considered a solid. By the effect of factors such as increased surface tension, freezing shrinkage and others, a freezing plastic meniscus 216 forms and extends or grows into the embryo ingot substantially along the wall of header plate 18. This causes the meniscus gap 210 to significantly increase thus curtailing heat flow out of the freezing plastic meniscus zone which is thus weakened especially at the innnermost portion 218. The freezing plastic meniscus then ruptures or fails probably at or near the inner portion 218 and liquid metal again lls the area behind the freezing meniscus restoring the submerged free liquid meniscus 220. The freezing metal surface which formed the freezing plastic meniscus 216 generally is not completely redissolved by this inrushing action and remains as a permanent discontinuity extending from the surface to a considerable depth into the solidified ingot.

In accordance with the invention, the solution to the problem of severe and disproportionate lap penetration resides in the provision of a ledge or surface such as 312 0r 412 in FIGURES 3 and 4, respectively. This surface appears to interrupt lap penetration or, at least, increase the extent to which the lap penetration redissolves when 1t ruptures. Another aspect is the diversion of incoming liquid metal running along the header plate wherein the metal stream running down along the surface 330 or 414, in FIGURES 3 and 4, is diverted to a more horizontal attitude. Two principal factors are involved in practicing the method of the invention. First, referring to FIGURE 1 as the gate opening 20 is smaller than the mold opening, molten metal is caused to move along the header plate wall 19 normal to the ingot axis; the ledge or surface 312 or 412 diverts this liquid metal surface stream or liow along the header plate such that it enters the mold at a significantly horizontal attitude rather than not being deflected until it actually reaches the mold. Second, the ledge or surface 312 or 412 diverts to some extent the direction of the lap growth toward the horizontal and in the direction opposite to ingot movement and incoming molten metal flow. This diversion or deliection of incoming liquid metal toward the horizontal and into the mold entrance together with the lap deflection likewise toward the horizontal but toward the opposite direction eifectively minimizes the disproportionate lap penetration at the lower ingot surface portions. At this point it should be Vunderstood that the theoretical discussions and explanations set forth as to the nature and cause of laps together with the mechanism by which the invention achieves its objects are merely intended to illustrate the invention with greater perspective and are not necessarily intended to place any limitation on the invention. The benets achieved by the invention are observable phenomena and need not be tied to any theory.

Turning to the apparatus aspects of the invention for convenience purposes in this description, the ledge cougurations shown in FIGURES 3 and 4 are described as having a base surface, 312 an-d 412 in FIGURES 3 and 4, respectively, and a back surface, 314 and 414. The inventive concept mainly resides in the provision of the base surface, the vback surface -being merely incidental in the broadest sense of accomplishing the objects of the invention. However, the back surface may be varied and will to an extent influence optimal results as descri-bed hereinafter.

The principal requirements for the base surface are 1) that it does not chill, i.e. remove significant heat from the molten metal, hence the term non-chilling base surface is descriptive, (2) that the base surface is substantially non-vertical, i.e. is inclined toward a horizontal attitude, (3) that the 'base surface be in close proximity inwardly from the inner wall surface of the chilled mold wall, and (4) that the ba'se surface be situated to the anterior of the chilled mold.

The most expedient way to render the base surface non-chilling is to fashion it from heat insulating or refractory material as indicated in FIGURES 3 through 7, for example 312 in FIGURES 3 and 6 where it forms part of a notch cut into the header plate 18 composed of a refractory material. However, lthis does not constitute a limit on the invention, for example, as indicated in FIG* URE 4b the base surface may be fashioned from an insert 416 which may be in a heat conducting material provided it is thermally insulated from the chilled mold as by that portion 417 of the header plate -disposed therebetween. It is recommended that the edge of the base surface 360 in FIG. 6 be fairly sharp and is preferably not rounded more than a %4 radius. In this respect the insert configuration of FIG. 4b offers some advantage in that the insert edge is less prone to erosion, etc., than most refractory materials.

The slope of the base surface may, generally speaking, vary from the horizontal (or substantially horizontal) attitude shown in FIGURE 4a to a condition where it diverges into the chilled mold at an angle of up to 45 or even more with respect to the mold axis. For example in FIGURES 3 and 6, the base surface 312 is shown diverging into the mold at an angle of about with respect to the mold axis; that is, angle x in FIGURE 6 is 20. For many alloys this value may approach the optimum. However, the slope can generally be increased to up to 45 without severely impairing the results. Further increases, i.e. a steeper slope, will generally result in somewhat poorer lap control for most light metals. However, angle x, if desired, may be increased to up to 60 without departing from the scope of this invention. A substantially horizontal slope often provides slightly inferior results as compared to a diverging slope in that such may introduce minor surface tearing. For most aluminum alloys a slope -diverging into the mold at from 15 to 25 will generally be found to provide the best results and in determining optimum conditions this slope range is the best starting point.

The base surface should be in close proximity to the chilled mold inside surface. Referring to FIGURE 6, the A dimension generally should not exceed 1/8, which for most aluminum alloys is considered a maximum; 3&2 is better than 1/16 is preferred although this-dimension may be as small as 0.010 and still confer some benefit within the practice of this invention. It should be understood that the A dimension is measured from the inside surface of any step such as 30 at the mold entrance as indicated in FIG. 6 since, as the step seldom exceeds 0.010" into the mold c-avity opening, its surface is considered the chilled mold inner wall surface at the mold entrance. Also as indicated above and shown in FIGURES 3 through 7, the base surface is to the anterior to the chilled mold entrance. In other words the surface should not extend to any significant extent into the mold, and hence the term substantially without is intended to express such.

The length or depth of the base surface, the B dimension in FIGURE 6, is somewhat less critical than the A dimension. However, some restraint is warranted for best results in that excessive depths, for example, where B exceeds 1A", while tending to alleviate excess lap penetrations in accordance with the invention, often do so at the expense of introducing other defects such as minor surface tearing and the like. Hence for best results the B dimension in FIGURE 6 most often ranges from about about im to about 3/16.

While minor deviations are tolerable, the base surface should describe a perimeter which is substantially parallel to the inside mold surface. Of course, closely maintaining a given A dimension will assure a high degree of parallelism. However, the perimeter described by the base surface need not necesarily be a closed perimeter. The base surface is only required around the zone of the periphery where the disproportionate and severe lap penetration prevails. The precise extent of this zone varies from case to case and is generally determined empirically although the conditions indicated in FIGURE 8 will generally be observed. For a rectangular ingot the base surface need be provided only across the bottom, up both sides and around the top corners as indicated by line 810 in FIGURE y8a. Similarly line `810 indicates the zone for circular and polygonal cross-sections is shown in FIGURES 8b and 8c. Of course, closing the perimeter described by the base surface will not impair ingot qual-1 ity and therefore the 'base surface perimeter may be closed or unclosed within the practice of the invention.

Concerning the back surface, as suggested in the drawings, the slope of the back surface, 414 and 314, respectively, in FIGURES 4 and 6, may vary somewhat within the practice of the invention. For instance in FIGURE 4 the back surface is shown as vertical, i.e. a plane normal to the mold axis. In FIG. 6 it is shown as converging into the mold at about 20 (angle y=20)` with respect to this plane. Preferably for most aluminum alloys angle y should not exceed 45 for, as the angle further int creased, the benefits of the invention diminish in that while lap defects are improved, considerable surface tearing may be encountered.

The included angle (angle z in FIG. 6) between the back and base surfaces is, of course, variable. However, for the FIGURE 6 notch configuration it is preferably about 75 to 110 to assure that the volume of metal contained therein is suicient to be effective although smaller angles may confer some benefit within the practice of the invention for some flight metals. A small (eg. 1/32") radius, 316 in FIG. 6, may be provided for stress distribution purposes. Of course, if the radius becomes relatively large, it may include substantially all the notch surfaces as shown in FIG-URE 7. In this case the recess or notch parameters generally speaking are subject to the same controlling or limiting factors as described above for the FIGURE 6 geometry, the angular dimensions. being measured tangentially. Typical values for A, B and R in FIGURE 7 are, respectively, 1/16, Ma and 1/8. Angles x and y are both about 20. Obviously in FIGURE 7 the demarcation between back and base surfaces is merely academic, one suitable delineation being line 713` bisecting the included angle z.

As suggested above, the optimum configurations and dimensions vary substantialy from case to case depending on casting variables such as alloy composition, ingot size, the specific characteristics of the chilled mold, etc. Thus for a given alloy composition being cast in a specific continuous horizontal casting apparatus -of the `general type described hereinbefore, the optimum configuration and its dimensions are readily determined using the general guide lines set forth in this description. While these optimum parameters will vary from case to case, it is often observed that the notch-like configuration shown in FIGURES 3 and 6 offers onsiderable advantages in the results obtained and convenience of construction, `and is therefore a preferred embodiment of the invention. To more clearly illustrate the practice of the invention the following examples will proceed.

Example 1 Ingots of an aluminum alloy, the nominal composition of which is 0.45% manganese, 4% magnesium, 0.10% chromium, the balance being aluminum and impurities, the ingots having rectangular cross-sections of about 16" by 39 were continuously cast in horizontal molds. Using lthe apparatus of the general type shown in FIGURE 1, but without the notch in the header plate, several ingots were cast of which all exhibited non-uniform lap defect depth in that the depth across the mid-top portion generally averaged less than /l" but the depth at the top corners, the sides and bottom, the zone designated 810 in FIG. 8a, was about 1% and sometimes more. Thus these ingots had to have l/iz minimum metal removed from each side scalped for further fabrication. In order to alleviate this severe and disproportionate lap penetration by the practice of the invention several configurations of varying dimensions were tested and many were found to significantly improve the lap condition. A notch configuration such as shown in FIGS. 3 and 6 was found to provide very good results and is easily constructed. Referring to FIG. 6, the included angle z of the notch was about 90. The notch depth b was about 1A and the base surface height A was 1/16". The base surface 312 had a slope, angle x, of about 20. Referring to FIGURE 8a the notch extended around a non-closed periphery corresponding to the zone 810 of severe and disproportionate lap penetration. Closing the periphery of the notch across the top-most portion of the ingot added little or no improvement for this particular portion. The aluminum alloy ingots so produced had a generally uniform lap penetration of about 3716 maximum and could be machined on any surface by cut of only 1A in depth.

This is contrasted to the need for removing at least l/2" of the surface on ingots produced by prior casting practice.

Example 2 penetration was observed in the ingot lower surface portions. This condition was alleviated by modifying the header plate in accordance With the configuration shown in FIGURE 4a. In this case the base surface 412 was horizontal and the lback surface 414 was vertical, or

normal to the horizontal mold axis, the surfaces thus describing a recess covering a-lmost the entire face of header plate 18. The base surface 412 was situated about 1/32" above the adjacent step provided by the oil ring 32. As indicated earlier, this step is considered the chilled inner mold wall surface at the mold entrance. The depth of :the base surface was about 1/16 to Ms. The improved ingots again exhibited a maximum lap penetration of abOLlt 5x16".

Example 3 Ingots were continuously cast in an aluminum alloy containing nominally 5.6% zinc, 1.6% copper, 0.30% chromium, and 2.5% ma-gnesium, the balance being aluminum and impurities. Using the same type of apparatus as that used initially in Example 1, the ignots first produced were again marked by severe and disproportionate lap penetration in the ingot lower surface portions. However, t-he provision of a notch configuration of the type delineated in Example 1 decreased the disproportionate lap penetration .generally by at least 50% and often to the extent that lap penetration was .practically nil.

Other configurations also offer promise and may even be preferred for some metals. For instance, the various figures show the base and back surfaces `as being machined on the header plate Wall, but other schemes immediately suggest themselves such as that shown in FIGURE 5 where 520 is a gasket-like member and when affixed to the header plate 18 describes base surface 512 and back surface 514. Also, it is to be understood that While extensive reference to aluminum and to particular alloys thereof appear in this description, such is not a limitation thereon. The invention will find application in the horizontal continuous casting of various light metals having a tendency to exhibit ydisproportionately deep lap defects in the lower ingot surface portions. By reference to the light metals is intended to mean aluminum and magnesium or their alloys containing at least base metal.

While there have been shown and described what are presently considered to be preferred embodiments of the invention together with some minor variation, further modifications thereto will readily occur to those skilled in the art. It is not desirous therefore that the invention be limited to the specific arrangements described and the appended claims are intended to include any modifications or variations as fall within the true scope and spirit of the invention.

What is claimed is:

1. An apparatus for the continuous casting of an ingot containing at least 75% aluminum comprising a molten metal reservoir, a horizontally disposed mold in communication with said reservoir, said mold having a chilled inner wall surface and an entrance and exit and having at its entrance a small inwardly extending step, a cornrnon non-chilling header plate between said reservoir and said entrance of said mold except for a gate opening in said header plate for the passage of molten metal from said reservoir to said mold, said gate opening being relatively small with respect to the cross section of the mold entrance and spaced inwardly from the inner mold Wall surface, a non-chilling base surface located substantially Without the entrance end of said chilled mold and disposed inwardly of but in close proximity to the inner mold wall surface, said base surface describing `a perimeter substantially parallel to that of the mold inner wall surface, the slope of the said non-chilling base surface ranging from (a) diverging into the mold at an angle of not more than 60 with respect -to the mold axis to (b) a slope substantially parallel to the mold axis, means for applying lubricant to the inner mold wall surface at the entrance portion of said mold and substantially around the periphery thereof, means for cooling said mold and the ingot within and emerging therefrom substantially around the periphery thereof, and means for withdrawing the ingot from the mold at a relatively con-tinuous rate.

2. An apparatus for the continuous casting of an ingot containing at least 75% aluminum comprising a molten metal reservoir, a horizontally disposed mold in communication with said reservoir, said mold having a chilled inner wall surface and an entrance and exit, and having at its entrance a small inwardly extending step, a common non-chilling header plate between said reservoir and said entrance of said mold except for a gate opening in said header plate for the passage of molten metal from said reservoir to said mold, said gate opening being relatively small with respect to the cross section of the mold entrance and spaced inwardly from the inner mold wall surface, a non-chilling base surface located without the entrance end of said chilled mold and disposed inwardly of the inner mold wall surface by from 0.010" to Ms, said base surface describing a perimeter substantially parallel to that of the inner mold wall surface, the slope of said non-chilling base surface ranging from (a) diverging into the mold at an angle of not more than 45 with respect to the mold axis, to (rb) a slope substantially parallel to the mold axis, means for applying lubricant to the inner mold wall surface at the entrance portion of said mold and substantially around the periphery thereof, means for coolin-g said mold and the ingot within and emerging therefrom substantially around the periphery thereof, and means for withdrawing the ingnot from the mold at a relatively continuous rate.

3. The apparatus as in claim 2 wherein the non-chilling base surface diverges into the chilled mold at a slope ranging from to 25 with respect to the mold axis.

4. The apparatus as in claim 2 wherein the non-chilling base surface is disposed inwardly of the inner mold wall surface by from 1/16 to 3/32.

5. Apparatus for the continuous casting of an ingot containing at least 75% -aluminum comprising a molten metal reservoir, a horizontally disposed mold in communication with said reservoir, said mold having a chilled inner wall surface and an entrance and exit and having at its entrance a small inwardly extending step, a common non-chilling header plate between said reservoir and said entrance of said mold except for a gate opening in said header plate for the passage of molten metal from said reservoir to said mold, said gate opening lbeing relatively small with respect to the cross section of the mold entrance and spaced inwardly from the inner mold wall surface, a non-chilling base surface loca-ted in said header plate and disposed inwardly of the inner mold wall surface 'by from 0.010" to 1/s, said base surface describing a perimeter substantially parallel to that of 4the inner mold wall surface, the slope of said non-chilling base surface ranging from (a) divergin-g into the mold at an angle of not more than with respect to the mold axis to (b) a slope substantially parallel to the mold axis, said base surface constituting the outer boundary of a recess in the header plate, the inner boundary being a back surface the slope of which Varies from (a) a plane normal to the mold axis to (b) converginginto the mold at an angle of not more than 45 with respect to said plane, means for applying lubricant to the inner mold wall surface at the entrance portion of said mold and substantially around the periphery thereof, means for cooling said chilled mold and the ingot within and emerging therefrom substantially around the periphery thereof, and means for withdrawing the ignot from the mold lat a relatively continuous rate.

6. The apparatus as in claim 5 wherein the non-chilling base surface is disposed inwardly of the inner mold wall surface by from 1/1 to 5732.

References Cited UNITED STATES PATENTS 1,448,359 3/1923 Dittman. 2,946,771 8/1961 Armand et al. 22-57.2 3,076,241 2/1963 Simonson et al. 22-57.2 XR

WILLIAM I. STEPHENSON, Primary Examiner, R. ANNEAR, Assistant Examiner. 

1. AN APPARATUS FOR THE CONTINUOUS CASTING OF AN INGOT CONTAINING AT LEAST 75% ALUMINUM COMPRISING A MOLTEN METAL RESERVOIR, A HORIZONTALLY DISPOSED MOLD IN COMMUNICATION WITH SAID RESERVOIR, SAID MOLD HAVING A CHILLED INNER WALL SURFACE AND AN ENTRANCE AND EXIT AND HAVING AT ITS ENTRANCE A SMALL INWARDLY EXTENDING STEPS, A COMMIN NON-CHILLING HEADER PLATE BETWEEN SAID RESERVOIR AND SAID ENTRANCE OF SAID MOLD EXCEPT FOR A GATE OPENING IN SAID HEADER PLATE FOR THE PASSAGE OF MOLTEN METAL FROM SAID RESERVOIR TO SAID MOLD, SAID GATE OPENING BEING RELATIVELY SMALL WITH RESPECT TO THE CROSS SECTION OF THE MOLD ENTRANCE AND SPACED INWARDLY FROM THE INNER MOLD WALL SURFACE, A NON-CHILLING BASE SURFACE LOCATION SUBSTANTIALLY WITHOUT THE ENTRANCE END OF SAID CHILLED MOLD AND DISPOSED INWARDLY OF BUT IN CLOSE PROXIMITY TO THE INNER MOLD WALL SURFACE, SAID BASE SURFACE DESCRIBING A PERIMETER SUBSTANTIALLY PARALLEL TO THAT OF THE MOLD INNER WALL SURFACE, THE SLOPE OF THE SAID NON-CHILLING BASE SURFACE RANGING FROM (A) DIVERGING INTO THE MOLD AT AN ANGLE OF NOT MORE THAN 60* WITH RESPECT TO THE MOLD AXIS TO (B) A SLOPE SUBSTAN- 